1. Field of the Invention
The present invention relates to a plasma processing apparatus for a very large area using a dual frequency, and more particularly, to a plasma processing apparatus for a very large area using a dual frequency, capable of improving plasma uniformity to the maximum extent to obtain a higher plasma density.
2. Description of the Prior Art
In general, an inductively coupled plasma (ICP) processing apparatus includes a spiral antenna installed at an upper outer portion of a reaction chamber, in which a plasma etching process is performed, with a dielectric substance interposed therebetween. The ICP processing apparatus applies radio-frequency (RF) induced power to the spiral antenna, induces an electric field in the reaction chamber, and thereby generates plasma. The ICP processing apparatus has a very simple structure compared to an electron cyclotron resonance (ECR) plasma processing apparatus or a helicon-wave excited plasma (HWEP) processing apparatus, and can generate the plasma over a large area in a relatively easy manner. For this reason, the ICP processing apparatus has been applied in various fields and research into ICP apparatuses is ongoing.
The construction of a chamber in a conventional ICP processing apparatus is illustrated in FIG. 1A and will be briefly described below.
An antenna source 100′ is disposed on the uppermost side centering around a chamber 300′ in such a manner that the antenna source 100′ is exposed to ambient air. A dielectric member 200′ is interposed between the antenna source 100′ and the chamber 300′ so as to insulate the antenna source 100′ from the chamber 300′ while maintaining a vacuum state. Further, an etching target 400′ is placed below the chamber 300′.
A spiral antenna source used for the chamber of the conventional ICP processing apparatus is illustrated in FIG. 1B.
However, as the volume and surface area of the etching target 400′ increase, such a spiral antenna source causes various problems.
First, if the chamber has a large area, the dielectric member for maintaining the vacuum state between the antenna source and the chamber considerably increases in size and thickness. Hence, the cost of production increases, and efficiency is lowered due to an increased distance between the antenna source and plasma.
In addition, because the reaction chamber has a large area, the antenna source also increases in length. Thus, loss of applied power due to resistance of the antenna increases, and an etch rate is lowered due to non-uniformity of the plasma
Moreover, when a power supply capable of applying power at a frequency of 13.56 MHz is used, a standing wave effect (two wave pulses having the same amplitude and frequency and propagating in opposite directions interfere to form standing waves) may occur at a half wavelength portion of the antenna source, so that the area of the chamber can no more be enlarged.
In order to solve these problems, the present applicant filed Korean Patent Application No. 2003-28849, titled “Inductively Coupled Plasma Processing Apparatus Having Internal linear Antenna for Large Area Processing,” and No. 2004-17227, titled “Inductively Coupled Plasma Apparatus Using Magnetic Field.” The constructions of the inventions disclosed in these two patent applications will be briefly described below.
First, as illustrated in FIG. 2, the inductively coupled plasma processing apparatus for a large area processing disclosed in Korean Patent Application No. 2003-28849 includes a reaction chamber 10, a plurality of linear antennas 32 that receive induced power, are horizontally arranged spaced apart from each other by a predetermined distance at an inner upper portion of the reaction chamber 10, and have adjacent first ends coupled to each other with a predetermined curvature at an outer portion of the reaction chamber 10, and at least one magnet 42 disposed adjacent to the linear antennas 32 so as to generate a magnetic field perpendicular to an electric field generated by the linear antennas 32 in such a manner that electrons move along spiral trajectories.
Here, the linear antennas 32 and the magnets 42 are enclosed by protective tubes 30 and 40 formed of quartz in order to prevent direct exposure to plasma, respectively. A reference number 20 indicates a stage on which a substrate to be etched (not shown) is loaded.
Next, as illustrated in FIG. 3, the inductively coupled plasma apparatus using a magnetic field disclosed in Korean Patent Application No. 2004-17227 includes a reaction chamber 110 provided with a stage 120 on which a substrate to be etched (not shown) is loaded, and at least one antenna source 4 having a plurality of antenna rods 410 and 420 that are alternately aligned in parallel, wherein the antenna rods 410 and 420 are each provided thereabove with a plurality of magnets.
Here, the antenna rods 410 and 420 and the magnets are also enclosed by protective tubes 130 and 140 formed of quartz, respectively, in order to prevent direct exposure to plasma.
Each antenna source 4 is connected to an RF induced power section 7 on one side thereof and is grounded on the other side thereof.
However, because the protective tubes for protection from the plasma are formed of quartz, they are easily corroded by corrosive gases. When the corrosion becomes serious, the tubes themselves are damaged and the vacuum state cannot be maintained. Such a situation can be very dangerous.
Further, when the antenna rods and the magnets are replaced, they are separated from the wall of the reaction chamber one by one and then assembled again. As such, the replacement work requires much time and furthermore is not easy.